The mother of James Blake, the tennis star who was slammed to the ground by an NYPD officer last week in an incident that prompted far-reaching condemnation, has suggested that race relations in America are getting worse, and admitted: “It seems there’s no end to racism in this country.”

Betty Blake wrote in Thursday’s New York Daily News a week after her son, a former world No 4, was knocked to the ground outside the Grand Hyatt in Manhattan by an NYPD officer in plainclothes. Blake was handcuffed, arrested and detained before officers admitted they had the wrong man. Blake said he did not want to suggest the incident was racially motivated but many felt the arrest raised broader questions about the NYPD’s mistreatment of minorities.

Betty Blake, who is white, was born in the UK and moved to the US at age 16. She raised two biracial sons with her black husband Thomas, and wrote in her piece: “I believe the great majority of people who read this story know it has to do with race. It seems there’s no end to racism in this country – in fact, it seems to get worse.

“We can legislate against it, but how do you eradicate it from people’s hearts? Where did the South Carolina murderer learn such hatred? Some parents still bring up their children to look on different races as inferior, and what you learn as a child tends to stay with you.”

Betty Blake, who is 80, said it was “impossible” for white people to understand what life for black Americans is like. “Long before I met Tom [my husband] I often pondered the racial situation in this country, especially during the two years I lived in Missouri, where segregation was still lawful. I had never encountered this in England. Hearing some of Tom’s experiences made me realize that as a Caucasian it’s impossible to empathize completely with the plight of an African-American in this country.”

James Blake said he felt “raw” after the arrest, and kept replaying the violent incident in his head. Officer James Frascatore, who tackled Blake to the floor, has been placed on desk duty, and stripped of his badge and gun. It has subsequently emerged that Frascatore has amassed a number of complaints for alleged excessive force.

Betty Blake wrote: “I felt guilt for having brought him into a world where this can happen — my beautiful son, who has experienced so much love and admiration, not just for his tennis prowess but for his character, taken down and humiliated by someone who apparently judged him only by his outward appearance.

NYPD commissioner Bill Bratton apologized to James Blake, and said the “arrest raised serious questions about [the officer’s] actions” but denied allegations of racism. “I don’t believe that race was a factor,” Bratton said. “This rush to put a race tag on it … I’m sorry, that’s not involved in this at all.”

James Blake said neither Frascatore nor any of the other officers at the scene identified themselves as police. Civil rights activists led a small protest on Thursday outside City Hall to call for Frascatore’s departure. Jerome Rice of the NAACP said: “This officer acted like the Lone Ranger. How many CCRB complaints should an officer have in their record? It’s unacceptable.”

Betty Blake praised her son for not resisting arrest, but wondered whether he was treated differently because he was a high-profile figure: “Would it have been swept under the rug as so many others are, some of which are now coming to light because of this incident. What about apologies to those people — not just the victims, but the families who also suffer? Just because James can hit a little yellow ball better than most, should he get special treatment? I thought we were all created equal.”